Oh No Syncro problem

[andrew muir]

Hi
Had the car out today (260z)
1st to 2nd Gear changes are cruntching really badly all other gears are working as normal.
Replaced the gearbox oil last week with Millers TRX semi synth, might have over filled it could this be the problem? Seems to be worse after car has warmed up.
Need this sorted fairly quick as I am suposed to be going to SPA in 5 weeks time.
Has the gearbox had it and what are my options for getting this sorted quickly?
Cheers
Andrew

 

[Rob Gaskin]

Andrew, you can drive a car with a poor synchro - that shouldn't stop you travelling.

Weak synchro on 2nd is common.

You will just have to match your revs to the gear better

How is your 'double de-clutch' technique?

So is it the oil-change that has brought on the problem? If so it might be worth trying something else.

No quick fix apart from buying or borrowing a good box.

 

[andrew muir]

Thanks Rob
When I changed the oil the old stuff was very dirty and the plug had a bit of iron fillings on it.
The car seemed fine untill today but have not driven it that much.
Today every time I rev it past 3000 and change to second the cruntching is painfull to hear. The only way to prevent it is to let the revs drop to almost tickover, as for double clutching I always seem to be better on down shifts rather than upshifts.
I do believe it to have gotten worse after oil change so open to ideas of wonder oils etc.
What is the supply and going price of reconditioned boxesetc???
Andrew

Andrew, you can drive a car with a poor synchro - that shouldn't stop you travelling.

Weak synchro on 2nd is common.

You will just have to match your revs to the gear better

How is your 'double de-clutch' technique?

So is it the oil-change that has brought on the problem? If so it might be worth trying something else.

No quick fix apart from buying or borrowing a good box.

 

[zbloke]

Drop the Millers TRX out and try some Redline MT90

 

[pmac]

Drop the Millers TRX out and try some Redline MT90

Or some snake oil maybe
Or sprinkle some magic "fairy dust " over it.

 

[andrew muir]

How much for one of your S14 kits?

Or some snake oil maybe
Or sprinkle some magic "fairy dust " over it.

 

[zbloke]

Or some snake oil maybe
Or sprinkle some magic "fairy dust " over it.

Both would work.....if you could find them

If the change has become worse since changing the oil then thats the first thing I'd look at

The Millers TRX is a GL4/GL5 which can cause problems with older type synchros

MT90 is a GL4 and better suited to older type synchros

The damage could already have been done though

 

[andrew muir]

Problem was not instant after changing oil, but the box does seem different.
Box was ok till yesterday, surly cannot have worn out syncro that quickly. Box has only done 50 miles since then.
Has anyone got a good spare box for sale???

 

[pmac]

How much for one of your S14 kits?

Not got one at the moment.
PM me to discuss but I cant do anything in the time frame you originally mentioned due to impending holidays etc.

 

[pmac]

Both would work.....if you could find them

If the change has become worse since changing the oil then thats the first thing I'd look at

The Millers TRX is a GL4/GL5 which can cause problems with older type synchros

MT90 is a GL4 and better suited to older type synchros

The damage could already have been done though

Tim the point I am making is a primitive Nissan box that is now around 40 years old is probably fcuked. The clue being Andrews description of what he saw when the drained the old oil out.

 

[JK240]

Hi Andrew,

Bad news, although I have been driving with a dodgy second gear synchro for ages now, pain in the ****, but it is liveable with. Mine is always worse coming down the box rather than going up. And I would like the Pmac solution too, just wife, kids, holidays, house, garden shed, etc, etc, all seem to have priority in the funding stakes

Fortunately furthest I am going in it this year will be Tatton not Belgium, have a good trip!!

 

[Rob Gaskin]

Andrew, change the oil (get it nice and hot first to drain it ALL) . Just put Halfords gearbox oil in it and try it.

In my early days I had a Hillman Imp and my Dad recommended using 'Molyslip' additive in the transaxle after he had rebuilt it:

Molybdenum disulfide - Wikipedia, the free encyclopedia

My mate was a mechanic at a 'Rootes' main dealer and he STRONGLY ADVISED AGAINST IT, he said that there transmission expert reckoned that it hindered the synchros working effectively. It was a friction reducer and they needed friction to match the speeds of the gears and synchro cones etc. Perhaps your Millers oil has an additive like Moly?

Yes the box will be worn (a furry drain plug is normal) so long term you will need to replace it, but for Spa you haven't got time (unless you are Johnny Palmer ).

Double de-clutching up the box is what lorry/bus drivers had to do. Between 1st and 2nd put the lever in neutral and release the clutch for a slit second (don't blip the throttle like you would on a down-change).

 

[andrew muir]

Yes Rob
I remember that stuff from a while back.
I am aware that the oil may be causing the issue.
The oil that came out was really old and dirty, like old engine oil, I am wondering if the new oil is too slippy and not spinning up the syncros? Or if the new oil has reacted somehow to the remains of the old oil ???
In the short term would agree and is cheap and easy to replace and try an oil till it works.
At least it may help others out in the future, will post my findings.
Is fitting a early ZX box a viable alternative for a 2+2???
And do they have an advantage over my original box?

 

[JK240]

Is fitting a early ZX box a viable alternative for a 2+2???

I was thinking along those lines too Andrew, but finding an early ZX box is still tricky, and even if you do, its still going to be quite an old box and not guaranteed to be that much better or have a particularly long life. The S14 when you can get one is probably the better option, newer and parts likely to be more reaily available for longer going forward. Just what I have discovered talking to people over the last year or so.

 

[Rob Gaskin]

If the gearbox oil was dirty how can that happen? I reckon someone may have already tried Molyslip which is black?

Boxes - I've had a few of varying types including early ZX. The condition is the most important thing for you and there aren't going to be many Z boxes in good nick on the secondhand market.

Really S13/14 is the only alternative to having a full rebuild (which would be expensive even if you could get the parts).

S13/14 - from my experience if they are well used they can whine between 45-50 in top (in my car that's not a problem). Synchros seem strong. As with anything like this you need to trust the source, get a warranty or in my case for my track car buy it cheap and risk it (but pulling boxes out is a pain).

 

[Ian Patmore]

S box the way for a modded S30, but for a standard S30, its a bit overkill. You can buy the parts to refurbish a '71B standard box and have change from what it costs for a S 'box kit.

Just putting options up...

 

[andrew muir]

Hi Ian
The syncros are hard to get and from what i can see are about 100quid each?
Going to try some Red line MT90 in the box tomorrow to see if that resolves the sticky syncro.

S box the way for a modded S30, but for a standard S30, its a bit overkill. You can buy the parts to refurbish a '71B standard box and have change from what it costs for a S 'box kit.

Just putting options up...

 

[SKiddell]

You can buy the parts to refurbish a '71B standard box and have change from what it costs for a S 'box kit.

Just putting options up...

But your still left with a box that even in perfect condition isnt a patch on a decent S14

S13/14 - from my experience if they are well used they can whine between 45-50 in top (in my car that's not a problem). Synchros seem strong. As with anything like this you need to trust the source, get a warranty or in my case for my track car buy it cheap and risk it (but pulling boxes out is a pain).

Which is why I inspect every one before using it, teeth wear/load patterns will show most issues....but any good engineer could do that
Of the 13 boxes we have done so far we havent had one that needed to come back, maybe the owners were just glad to have a decent modern box rather than a stick in a bucket.

 

[andrew muir]

Totally agree, have you got one for sale as a kit? if so how much?

But your still left with a box that even in perfect condition isnt a patch on a decent S14



Which is why I inspect every one before using it, teeth wear/load patterns will show most issues....but any good engineer could do that
Of the 13 boxes we have done so far we havent had one that needed to come back, maybe the owners were just glad to have a decent modern box rather than a stick in a bucket.

 

[pmac]

Totally agree, have you got one for sale as a kit? if so how much?

Andrew I have already said.........

Not got one at the moment.
PM me to discuss but I cant do anything in the time frame you originally mentioned due to impending holidays etc.

Its a joint effort between us

I will PM you a reply tomorrow to the one you sent me